Compacting lead sludges



March 27, 1956 C. L. HOBBS, JR

COMPACTING LEAD SLUDGES 2 Sheets-Sheet 1 Filed Oct. 24, 1952 INVENTOR CHARLES L. HOBBS JR.

BY mw ATTORNEY March 27, 1956 C 1 0555, JR 2,739,526

COMPACTING LEAD SLUDGES Filed Oct. 24, 1952 2 Sheets-Sheet 2 .ZQg 6. f A

66 50 fljz 5 +54 L. 4 -4- L I ll 60 TION r 60 POSITION n 60/ POSITIONlIl POSITION IY INVENTOR CHARLES L.HOBB5,JR.

BY Mgm ATTORNEY COMPACTHNG LEAD SLUDGES Charles L. Hobbs, In, Wilmington, Del., assignor to E. l. du Pont de Nemours and Company, Wilmington, Dee, a corporation of Delaware Application October 24, 1952, Serial No. 31o,653

14 Claims. ((11. 100-437) This invention relates to a process for compacting anhydrous lead sludges, particularly sludges such as are formed in the manufacture of tetraethyl lead.

Tetraethyl lead has been manufactured in the past by the reaction of an excess of ethyl chloride with an alloy of lead and sodium. In such a reaction, most of the sodium of the alloy is converted to sodium chloride, about of the lead in the alloy is converted to tetraethyl lead, and most of the rest of the lead is converted to metallic lead in finely-divided form. Thus, when the yield of tetraethyl lead is from about 80% to about 98% of the quantity theoretically formed from the sodiumlead alloy according to the equation the reaction mass consists essentially of finely-divided lead, from about 0.36 to about 0.38 part by weight of finely-divided sodium chloride per part of lead, from about 0.4 to about 0.5 part by weight of tetraethyl lead per part of lead, a small amount of unreacted alloy, and the excess ethyl chloride.

After the reaction is completed, most of the excess ethyl chloride is distilled from the reaction mass, the reaction mass is drowned in water which converts any unreacted alloy to lead and sodium hydroxide, and the tetraethyl lead is removed therefrom by steam distillation, leaving a suspension of finely-divided lead in a dilute aqueous solution of sodium chloride and sodium hydroxide. Such a suspension is then conveyed to a sludge pit where it is allowed to settle to form an upper layer of the aqueous solution and a lower layer of aqueous sludge which comprises the lead mixed with from about 8% to about 20% by weight of the aqueous solution. The water layer is drawn oil and the aqueous sludge is washed with water to remove most of the salt, then dried to remove most of the water, and the resulting lead is refined by melting in a reverberatory furnace at about 700 C. to about 900 C.

Such a process of handling the lead sludge is expensive and hazardous throughout, because of the presence of residual tetraethyl lead therein. It requires extensive facilities in the form of sludge pits, driers, furnaces and equipment for handling the sludge, and large amounts of heat. Recently, there have been developed continuous processes for carrying out the reaction and manufacturing tetraethyl lead, which further complicate the handling of the sludge and the recovery of the lead therefrom. Some of such continuous processes include the continuous steam distillation of both the tetraethyl lead and the ethly chloride from the reaction masses.

During the handling of the lead sludge by such processes and, particularly, during the distillation and washing procedures, the surfaces of the lead particles become oxidized. In some cases, the amount of such lead oxide may be less than 1% by weight of the lead and, in severe cases, may be as much as 20% to but usually will constitute from about 2% to about 10% by weight, covering the surfaces of the pieces and particles of lead.

Handling, transportation and storage of finely-divided lead is difiicult and results in a great amount of oxidation of the lead. While the presence of such lead oxide does not affect the compacting of the lead, it is objectionable in the subsequent refining of the lead. Accordingly, it is desirable to avoid such oxidation of the lead. The ethyl chloride, recovered by steam distillation contains water and must be carefully dried before it is returned for reaction with lead-sodium alloy. Furthermore, there is some hydrolysis of ethyl chloride during steam distillation, resulting in loss of some of the ethyl chloride and requiring costly purification.

It is an object of the present invention to provide an improved and simplified method for separating most of the solids and the liquids in tetraethyl lead reaction masses which does not involve steam distillation and which avoids the disadvantages thereof. Another object is to provide a method therefor which comprises compacting anhydrous lead sludges. A further object is to provide a method of such character which is particularly adapted for the treatment of anhydrous lead sludges that are formed in the manufacture of tetraethyl lead. A still further object is to provide a process which is particularly adapted. to be operated as a part of an integrated process in which all steps in the manufacture of tetraethyl lead and the recovery of the by-products are operated continuously. Still other objects will appear hereinafter.

The above and other objectsmay be accomplished in accordance with my invention which comprises introducing between opposing solid pressure members of an expressing device an anhydrous lead sludge which consists essentially of a mixture of finely-divided lead, from about 0.36 to about 0.38 part by weight of finely-divided sodium chloride to each part of lead, and from about 5% to about 65% by weight of a liquid which is a member of the class consisting of tetraethyl lead and mixtures of tetraethyl lead and a volatile organic solvent for the tetraethyl lead which boils below C., compressing the sludge between such members under a pressure of from 150 to about 20,000 pounds per square inch, and separating from the compacted solids any liquid that is expressed from the sludge during such compression.

While such sludges are, in general, sufiiciently fluid to flow through wide pipes and funnels by gravity alone and to flow under slight pressures into the compression chamber of a press, particularly when the lead and the salt are in finely-divided form and the mixtures contain 8% or more liquid, they are not forced out from between the pressure members during compression. Thereby, substantially all of the solid particles are subjected to the pressure of the pressure members and compressed into compacted form as solid, coherent sheets, strips, flakes or pellets, and usually the major proportion of the liquid is squeezed out of the sludge in anhydrous form. The liquids in the sludges prevent substantial contact of the finely-divided lead with oxygen and the mixture of lead and salt and in the compacted form, is resistant to oxidation. Therefore, the compacted proclucts can be readily handled, transported and stored without substantial change due to oxidation. Also, it could not be predicted that the large amounts of salt, from about 36% to about 38% of the weight of the lead, would not prevent the compressing of the mixture into solid, coherent masses.

The resulting compacted lead product is of a character which is particularly suitable for refining to recover pure lead therefrom, particularly since it contains little or no lead oxide. In the refining process, it will usually be crushed and then melted, preferably in the presence of molten caustic soda, and the molten lead separated from the salt and any infusible material.

The process of my invention may be carried out in a wide range of equipment, as by feeding the sludge (a) into the nip of a pair of oppositely rotated rolls which will compact the solids into strips, sheets or flakes and expel the liquid as the material is drawn between the rolls; or (1)) into a chamber or confined space, such as a die or cylinder, wherein it can be subjected to pressure from reciprocating rams or plungers to expel the liquid and compact the solids into pellets or blocks; or (c) by pressing the sludge between horizontal plates.

Representative types of apparatus suitable for carrying out the process of my invention are shown in the accompanying drawings in which;

Figure l is a side viewof, one type of suitable apparatus, i P r s broken aw y for clearness of illustration;

Figure 2 is a perspective. view of a second type of suitable apparatus, \vith parts omitted for clearness of illustration;

Figure 3 is a front view of a third and. preferred type of apparatus, with parts broken away for clearness of illustration;

Figure 4 is an enlarged front view of a ram of the apparatus of Figure 3;

Figure 5 is an end view of the ram of Figure 4; and

Figure 6 is a diagrammatic illustration of the diiferent positions of the rams in the operation of the apparatus of Figure 3.

Referring to Figure l, a cylindrical die-10, having an internal diameter of about 0.75 inch and a, height of about 6 inches is supported on a ring 12 mounted upon a lower press platen M. A bottom plunger 16, also supported by the ring 12, fits loosely in the lower end of the die. A top plunger 18. is mounted on the, lower surface of an upper press platen 20, and has an external diameter of about 0.004 inch to about 0.006 inch less than the internal diameter of the die and fits loosely into the upper end of the die. It will be understood that the size of the die may be widely varied, with corresponding variations in the sizes of the cooperating parts.

In operation, the die, bottom plunger and supporting ring are placed in position as shown in Figure l, with the top plunger raised above the die. A charge of sludge is placed in the die to partially fill it, usually to a height of about 1 to about 5 inches. The pressplatens are moved toward each other to introduce the top plunger into the top of the die, into contact with the sludge, and then to compress the sludge under the desired pressure. During such compression, the liquid is squeezed out of the sludge t Referring to Figure 2, smooth steel rolls 22 and 24v are mounted in journal bearings 26 and 28 at each end and are rotated in opposite angular directions, as shown by the arrows on the ends thereof, by gearing 30. The journal bearings 26 are forced toward journal bearings 28 by heavy springs 32011 adjusting screws 34, so as to force the rolls 22 and 24 into close contact under pressures controlled by adjustment of the springs. As so far described, the apparatus is similar to roll drills for milling rubber and other materials, and it will be understood that the journals 26 and 28 and adjusting screws 34 will be mounted and supported in a suitable frame'in aconventional manner. Since such a frame and the methods and means for supporting the operating parts therein are conventional and, well known to the art, that structure has been omitted so as to enable the essential operating parts to be more clearly shown.

A feed box is mounted over the rolls and consists of side walls 36 and end walls 33. The side walls 36 extend for substantially the length of the rolls and fit closely on top thereof, preferably, in the vertical planes of the axes of the rolls. The side walls may be shorter and may be set closer together, but may not extend beyond the ends of the rolls. The lower portions of the end walls extend down between the rolls, substantially to the point of contact of the rolls with each other, and have their bottom edges formed to closely fit against the upper inner quadrants of the rolls. Thus, the rolls form the bottom of the feed box.

A pipe 40 is provided for feeding sludge to the feed box. A pipe 42 has an end immersed in the liquid layer 44 in the feed box and is connected to a vacuum receiver, not shown. A pan or tank 46 is positioned below the mill to receive the compacted lead 48' and a minor proportion of the liquid.

In operation, the rolls are rotated andsludge: is continuously fed into the feed box through pipe 40; Theslud'ge enters the nip of the rolls which compacts the mixture of particles of lead and salt into. discontinuous sheets, strips or flakes 48, and expels the liquid therefrom. Mostof the liquid, squeezed out of the sludge, is retained in the feed box and forms the layer 44, substantially free. of. solids, on top of the sludge. That layer of expelled liquid is continuously drawn off through the vacuum line 42.

Referring to Figures 3 to 6, inclusive, which represents the preferred apparatus for commercial operation of. my invention, the apparatus comprises apress having anelongated cylindrical chamber and two opposed rams operating therein to rapidly form compacted: pellets. The cylindrical chamber 50 is formed, in parhby the bore of the horizontal cross portion 52 of. an inverted T-shaped member. The vertical portion 54- is connectedto a feed pipe 56 for the sludge. The bore. of the portion 54 and of the feed pipe 56 may be smaller or larger than the bore of portion 52, but, preferably, will: be of. substantially the same diameter. The cylindrical chamber Ellis extended slightly to the. left as shown at 58 so that the discharge outlet 60 of the chamber is spaced inwardly of the wall of thechamber 72. Also, the outlet 60 is spaced from the sludge inlet to the chamber 50 by a distance somewhat greater than the length of the largest charge of sludge.

A ram 62 has a sliding fit inthe right-hand portion of theillustrated cylindrical chamber 50 and is reciprocated' in said chamber through a hydraulic (or pneumatic) cylinder 64. An opposing ram 66 has asliding fit in the left-hand portion of the cylindrical chamber 50 and is reciprocated therein through a hydraulic (or pneumatic) cylinder 68. The ram 66-is provided with a plurality of small longitudinal grooves '70 in its cylindrical surface, which grooves extend from the end of the ram backwardly for a distance equal to at least /2 the distance between the outlet 60 and the sludge inlet to the chamber 50 and, preferably, slightly greater than the distance between the outlet and the sludge inlet. The number, size and form of the grooves 70may be. widely varied, provided that they do not greatly reduce the area of the end of the ram. Similar grooves may be provided on ram 62, if desired.

The, extension 58 is enclosed in a relatively large chamber 72, the lower end of which is in, the form of a chute connected with a liquiddischarge pipe, 74. A pellet discharge chute 76 extends upwardly through the bottom. of the chamber 72 and hasitsupper and positioned under outlet 60. A sliding cover 78 fits overv the upper end of the chute 76 and is intermittently operated to uncover that end of the'chute 76 by a cylinder rod and a The operation of the apparatus of Figures 3 to 5-' will be best understood by reference to Figure 6 which illus trates the'operation and successivepositions' of the rams.

The rams 62 and 66 will be in position I, with their ends on opposite sides of the sludge inlet opening of the cylindrical chamber 50, whereupon the sludge will flow by gravity into the space between the ends of the rams. The distance between the ends of the rams may be varied conveniently up to about 12 inches, so as to vary the size of the charge and of the pellets as desired, but preferably, will be substantially equal to the diameter of the sludge inlet of the cylindrical chamber. The rams 66 and 62 are then moved together in the direction of the arrows to position 11, which will bring the charge of sludge to a compression zone intermediate the outlet 60 and the sludge inlet of the chamber 50. At this point, the motion of ram 66 will be stopped or reversed as shown in position III, to compress the charge, to expel the liquid, and to press the particles of lead and salt together into a dense compacted pellet. Most of the expelled liquid passes along the grooves 70 in ram 66, through the outlet 60 and into the chamber 72, but is prevented from entering chute 76 by the cover 78. Little or no solid particles pass out with the expelled liquid even though the grooves 70 are much larger than such particles, such particles usually having diameters in the range of to 50 microns with some smaller than 10 microns. When the compression has been completed, the rams are moved to the left to position IV to bring the pellet beyond the outlet 60, the ram 66 moving faster and further than ram 62 so as to release the pellet and permit the pellet to drop. The cover 78 is moved to uncover the chute 76 after the compression step and before the pellet reaches the outlet 60, whereby the pellet drops into the chute 76. Then the cover 78 is moved to close the chute 76 and the rams are returned to position I to receive a new charge of sludge, and the cycle of operation is repeated.

Such apparatus and process are controlled automatically and operate at a rapid rate so that they are particularly well adapted for commercial use in a continuous process for making tetraethyl lead and the sludge. For large scale commercial use, the apparatus will ordinarily be of larger size, for example, such that the charge of sludge in the compression chamber will be about 12 inches long and about 12 inches in diameter.

The apparatus of Figures 3 to 6, inclusive, is not part of my invention but was invented by Daniel P. MacMurray and is disclosed and described in more detail in his application Serial No. 292,641, filed June 10, 1952, which became Patent No. 2,697,979 on December 28, 1954.

The reaction masses, obtained by the known batch process, ordinarily will contain from about 19% to about 23% by weight of tetraethyl lead and from about 16% to about 14% by weight of ethyl chloride, a total of from about 35% to about 37% by weight of liquid. Part or all of the ethyl chloride may be distilled oif before treating the mixture by the process of my invention. However, such reaction masses are preferably treated as produced, as the ethyl chloride is a good solvent for the tetraethyl lead and will aid in the removal of the tetraethyl lead from the solids during the pressing.

The reaction masses, obtained by the continuous processes, ordinarily contain from about 9% to about 4% by weight of tetraethyl lead and from about 68% to about 82% by weight of ethyl chloride, a total of from about 77% to about 86% by weight of liquid. In some cases, the proportion of ethyl chloride may be much higher and that of the tetraethyl lead correspondingly less. Before treating such continuously produced reaction masses by the process of my invention, the proportion of liquid must be reduced to 65 or less, preferably to from about 21% to about 51%. This may be accomplished by distilling off ethyl chloride to the desired extent but, preferably, is accomplished by decantation or filtration so as to remove part of the tetraethyl lead dissolved in the ethyl chloride. All of the ethyl chloride may be removed from the reaction mass by distillation iii or, preferably, by decantation or filtration followed by distillation.

The presence of tetraethyl lead in the compacted solids presents a hazard in the subsequent processing of such solids to recover the lead therefrom. Therefore, it is frequently desirable to reduce the amount of tetraethyl lead in the mixture as far as is practical before treating it by the process of my invention. Considerable amounts of the tetraethyl lead are firmly adsorbed on the particles of lead and cannot be completely removed by extraction with a solvent unless such extraction is continued to an impractical extent. However, the amount of tetraethyl lead in the mixtures can be materially reduced by a moderate washing of the mixture with a neutral inert solvent for the tetraethyl lead. Such solvents should be volatile organic solvents which boil below C. Such solvents are well known in the art and include halogenated hydrocarbons, aromatic hydrocarbons, aliphatic hydrocarbons, alcohols, ethers, and ketones. Ethyl chloride and benzene are particularly valuable, but ethyl chloride is the preferred solvent. At times, it is desirable to first compact the sludges by the process of my invention, then to crush or pulvarize the compacted solids, then to wash the crushed material with a solvent to more completely remove the tetraethyl lead from the solids, and then to again compact the solids by the process of my invention. When the mixtures are washed with a solvent, sufficient solvent must be left in the mixture to provide from about 5% to about 65% of liquid in the mixture. Ordinarily, at least the minimum amount of solvent will be retained by the particles of lead and salt when excess solvent is removed from the mixture solely by decantation or filtration.

Generally, the lead and the salt in the sludge will be in finely-divided form, i. e. particles not materially larger than about 1 millimeter (1000 microns) in diameter. The maximum permissible size of the particles will be limited by the size and capacity of the equipment in which the sludge is to be handled and compressed. As originally produced in the manufacture of tetraethyl lead, most of the particles of lead and salt in the sludge will be between about 10 and about 50 microns in diameter, with some even smaller. However, during the handling of the sludge, particularly with much agitation, a small proportion of the lead will frequently become agglomerated into larger particles up to about 1 millimeter in diameter and sometimes up to 1 centimeter. These larger particles of lead do no harm, unless the passages in the equipment through which the sludge is to be passed, are so small that such particles will clog such passages. When compacted material is ground for washing with a solvent followed by a second compacting step, the ground particles should have diameters in the range of from about 10 to about 1000 microns, preferably from about 10 to about 50 microns.

The process of my invention requires pressures of at least 150 pounds per square inch. The pressure employed will depend upon the results desired. At pressures of 150 p. s. i. and above, the particles of lead and salt are compacted into solid, coherent cakes, pellets, sheets, strips, flakes, and the like which can be readily stored and transported without danger of substantial change due to oxidation. However, the time required to obtain maximum compression, and the amount of liquid retained in the compacted solids, will decrease with increase in the pressure. When formed under 150 p. s. i., the compacted solids will retain up to 20% by weight of liquid and, if the mixture which is compressed under such pressure does not contain more than 20% of liquid, little or no liquid will be expressed from the sludge. Under a pressure of 600 p. s. i., the compacted solids will retain about 6.7% by Weight of liquid. The use of pressures in the range of 150 to 600 p. s. i. is frequently desirable where maximum compression isnot, necessary and where storage, or transportation, or both are desired or necessary, as when the production of the reaction masses exceeds the capacity of available higher pressure equipment, or when the higher pressure equipment is being cleaned or repaired, or where the compacted masses are to be crushed and washed with a solvent, or where highly porous masses are desired, or for other reasons. Most frequently, it will be desirable to remove as much as is practical of the liquid from the solids, and, for such purpose, the pressures employed will usually be from about 1,000 p. s. i. to about 10,000 p. s. i. and, preferably, from about 1,250 p. s. i. to about 5,000 p. s. i. Increase in pressure, above 10,000 p. s. i., has little effect to further reduce the liquid content of the compacted solids and hence will not ordinarily be justified from an economic standpoint. Pressures materially above 20,000 p. s. i. may be used, but they usually require large and uneconomically heavy apparatus so that they ordinarily will not be desired.

Usually, it will be most convenient to compress the sludge at atmospheric temperatures, although any temperatures between the freezing point of the liquid phase of the sludge and 100 C. are operable. When ethyl chloride or other volatile organic solvent is present, its loss may be prevented by operating at a temperature below its boiling point, or at higher temperatures by maintaining the expressed liquid under a corresponding higher pressure, or by recovering its vapor.

In order to further illustrate my invention, preferred modes of carrying the same into effect and the advantageous results to be obtained thereby, the following examples are given:

Example 1 Tetraethyl lead was made in conventional equipment by the reaction of 57 grams of sodium-lead alloy sodium) and 200 ml. of liquid ethyl chloride at 90 C. for 5 minutes under pressure. Ethyl chloride was then allowed to distill oil. The apparently dry reaction mass consisted of about 40 grams of lead, about grams of sodium chloride, about 16 grams of tetraethyl lead, and a small amount of ethyl chloride (about 21% by weight of liquid). The solid particles had an average diameter of about 50 microns. Such reaction mass was charged into the apparatus of Figure 1 and compressed under a pressure of about 5000 p. s. i. for two minutes at room temperature. The cylindrical pellet formed had a height of about 1.5 inches, a density of about 4.5 grams per cc., contained about 1.7 grams (about 3.1%) of tetraethyl lead, was dull gray in color, and was easily broken and crushed. The expressed liquid contained some ethyl chloride and 14.3 grams of tetraethyl lead, corresponding to a yield of about 89.3% of the tetraethyl lead in the reaction mass.

Example 2 A reaction mass, made from sodium-lead alloy (NaPb, containing 10% of sodium) and an excess of ethyl chloride, contained (after allowing the solids to settle and draining oit the supernatant solution of tetraethyl lead in liquid ethyl chloride) 67 parts by weight of finely-divided metallic lead, 25 parts of sodium chloride closely associated with the lead, 90 parts of liquid. ethyl chloride, and 7.0 parts of tetraethyl lead (about 51% by weight of liquid). The solid particles had an average diameter of about 50 microns. This semi-solid mass was intro duced into a press like the one used in Example 1 in charges of about 20 grams each, filling the die chamber to a height of about 1.75 inches. Each charge was subjected to a pressure of about 1250 p. s. i. for 20 seconds, forming a short cylindrical pellet about 0.25 inch high which weighed about 10 grams. The expressed liquid contained all of the remaining tetraethy-l lead and ethyl chloride, except about 0.3 part tetraethyl lead and about 2.7 parts-ethyl chloride which remained in the compressed pellets, i. e. the pellets contained about 3.26% liquid.

The pellets were pulverized to about 50 mesh and made into a slurry with an equal weight (about'95 grams) of liquid ethyl chloride and again pressed as before. residual tetraethyl .lead .in the pellets was reduced to less than 0.1 part, the rest being recovered from the ethyl chloride obtained in the second pressing. The pellets obtained were compact but readily broken and pulverized.

Example 3 Tetraethyl lead was made from 53.7 grams of alloy as in Example 1. After removal'of the unreacted ethyl chloride, the reaction mass was washed with grams of benzene, which was then filtered off. The mixture of lead, saltand benzene was then pressed as in Example .1, giving an additional amount of tetraethyl lead dissolved in benzene. The total tetraethyl lead recovered was 16.4 grams or 87.1% of the theoretical amount, based on the alloy added. The compressed material was similar .in appearance and physical properties to that formed in the other examples.

It will be understood that the apparatus and embodiments, disclosed in the drawings and given in the examples, are included merely for purposes of illustration and that my invention is not limited to the specific apparatus and embodiments so disclosed. On the other hand, it will be readily apparent that many variations can be made in the size, character and construction of the equipment'employed, and in the details and conditions of carrying out the process, without departing from the spirit or scope of my invention, as herein disclosed and as defined in the appended claims.

I claim:

1. The process for recovering a mixture of lead and salt in a compacted form from an anhydrous sludge consisting essentially of finely-divided lead, from about 0.36 to about 0.38 part by weight of finely-divided sodium chloride to each part of lead, and from about 5% to about 65% by weight of a liquid which is a member of the class consisting of tetraethyl lead and mixtures of tetraethyl lead and a volatile organic solvent for the tetraethyl lead which boils below C., which process comprises introducing said sludge between opposing solid pressure members of an expressing device, compressing the sludge and compacting thesolids between such members under a pressure of from 150 to about 20,000 pounds per square inch, and separating from the compacted solids any liquid expressed from the sludge during the compressron.

2. The process for recovering a mixture of lead and salt in a compacted form from an anhydrous sludge consisting essentially of finely-divided lead, from about 0.36 to about 0.38 part by weight of finely-divided sodium chloride to each part of lead, and from about 5% to about 65% by weight of a liquid which is a member of the class consisting of tetraethyl lead and mixtures of tetraethyl lead and a volatile organic solvent for the tetraethyl lead which'boils below 150 -C., which process comprises introducing said sludge between opposing solid pressure members of an expressing device, compressing the sludge and compacting the solids between such members under a pressure of from about 1,000 to about 10,000 pounds per square inch, and separating from the compacted solids any liquid expressed from the sludge during the compression.

3. The process for recovering a mixture of lead and salt in a compacted form from an anhydrous sludge consisting essentially of finely-divided lead, from about 0.36 to about 0.38 part by weight of finely-divided sodium chloride to each part of lead, and from about 5% to about 65% by weight of a liquid which is a member of the class consisting of tetraethyl lead and mixtures of tetraethyl lead and a volatile organic solvent for the tetraethyl lead which boils below 150 C., which process comsure members of an expressing device, compressing the sludge and compacting the solids between such members The 9 under a pressure of from about 1,250 to about 5,000 pounds per square inch, and separating from the compacted solids any liquid exprc sed from the sludge during the compression.

4. The process for recovering a mixture of lead and salt in a compacted form from an anhydrous sludge consisting essentially of finely-divided lead, from about 0.36 to about 0.38 part by weight of finely-divided sodium chloride to each part of lead, and from about 21% to about 51% by weight of a liquid which is a member of the class consisting of tetraethyl lead and mixtures of tetraethyl lead and a volatile organic solvent for the tetraethyl lead which boils below 150 C., which process comprises introducing said sludge between opposing solid pressure members of an expressing device, compressing the sludge and compacting the solids between such members under a pressure of from about 1,250 to about 5,000 pounds per square inch, and separating from the compacted solids any liquid expressed from the sludge during the compression.

5. The process for recovering a mixture of lead and salt in a compacted form from an anhydrous sludge consisting essentially of finely-divided lead, from about 0.36 to about 0.38 part by weight of finely-divided sodium chloride to each part of lead, and from about to about 27% by weight of tetraethyl lead, which process comprises introducing said sludge between opposing solid pressure members of an expressing device, compressing the sludge and compacting the solids between such members under a pressure of from 150 to about 20,000 pounds per square inch, and separating from the compacted solids any tetraethyl lead expressed from the sludge during the compression.

6. The process for recovering a mixture of lead and salt in a compacted form from an anhydrous sludge consisting essentially of finely-divided lead, from about 0.36 to about 0.38 part by weight of finely-divided sodium chloride to each part of lead, and from about 5% to about 27% by weight of tetraethyl lead, which process comprises introducing said sludge between opposing solid pressure members of an expressing device, compressing the sludge and compacting the solids between such members under a pressure of from about 1,000 to about 10,000 pounds per square inch, and separating from the compacted solids any tetraethyl lead expressed from the sludge during the compression.

7. The process for recovering a mixture of lead and salt in a compacted form from an anhydrous sludge consisting essentially of finely-divided lead, from about 0.36 to about 0.38 part by weight of finely-divided sodium chloride to each part of lead, and from about 5% to about 65% by weight of a mixture of tetraethyl lead and a volatile organic solvent for the tetraethyl lead which boils below 150 C., which process comprises introducing said sludge between opposing solid pressure members of an expressing device, compressing the sludge and compacting the solids between such members under a pressure of from 150 to about 20,000 pounds per square inch, and separating from the compacted solids any liquid expressed from the sludge during the compression.

8. The process for recovering a mixture of lead and salt in a compacted form from an anhydrous sludge consisting essentially of finely-divided lead, from about 0.36 to about 0.38 part by weight of finely-divided sodium chloride to each part of lead, and from about 5% to about 65% by weight of a mixture of tetraethyl lead and a volatile organic solvent for the tetraethyl lead which boils below 150 C., which process comprises introducing said sludge between opposing solid pressure members of an expressing device, compressing the sludge and compacting the solids between such members under a pressure of from about 1,000 to about 10,000 pounds per square inch, and separating from the compacted solids any liquid expressed from the sludge during the compression.

9. The process for recovering a mixture of lead and salt in a compacted form from an anhydrous sludge consisting essentially of finely-divided lead, from about 0.36 to about 0.38 part by weight of finely-divided sodium chloride to each part of lead, and from about 5% to about 65% by weight of a mixture of tetraethyl lead and ethyl chloride, which process comprises introducing said sludge between opposing solid pressure members of an expressing device, compressing the sludge and compacting the solids between such members under a pressure of from to about 20,000 pounds per square inch, and separating from the compacted solids any liquid expressed from the sludge during the compression.

10. The process for recovering a mixture of lead and salt in a compacted form from an anhydrous sludge consisting essentially of finely-divided lead, from about 0.36 to about 0.38 part by weight of finely-divided sodium chloride to each part of lead, and from about 5% to about 65% by weight of a mixture of tetraethyl lead and ethyl chloride, which process comprises introducing said sludge between opposing solid pressure members of an expressing device, compressing the sludge and compacting the solids between such members under a pressure of from about 1,000 to about 10,000 pounds per square inch, and separating from the compacted solids any liquid expressed from the sludge during the compression.

11. The process for recovering a mixture of lead and salt in a compacted form from an anhydrous sludge consisting essentially of finely-divided lead, from about 0.36 to about 0.38 part by weight of finely-divided sodium chloride to each part of lead, and from about 21% to about 51% by weight of a mixture of tetraethyl lead and ethyl chloride, which process comprises introducing said sludge between opposing solid pressure members of an expressing device, compressing the sludge and compacting the solids between such members under a pressure of from 150 to about 20,000 pounds per square inch, and separating from the compacted solids any liquid expressed from the sludge during the compression.

12. The process for recovering a mixture of lead and salt in a compacted form from an anhydrous sludgeconsisting essentially of finely-divided lead, from about 0.36 to about 0.38 part by weight of finely-divided sodium chloride to each part of lead, and from about 21% to about 51% by weight of a mixture of tetraethyl lead and ethyl chloride, which process comprises introducing said sludge between opposing solid pressure members of an expressing device, compressing the sludge and compacting the solids between such members under a pressure of from about 1,000 to about 10,000 pounds per square inch, and separating from the compacted solids any liquid expressed from the sludge during the compression.

13. The process for recovering a mixture of lead and salt in a compacted form from an anhydrous sludge consisting essentially of finely-divided lead, from about 0.36 to about 0.38 part by weight of finely-divided sodium chloride to each part of lead, and from about 5% to about 65 by weight of a liquid which is a member of the class consisting of tetraethyl lead and mixtures of tetraethyl lead and ethyl chloride, which process comprises washing the sludge with a volatile organic solvent for the tetraethyl lead which boils below 150 C., incompletely separating the solvent from the mixture of lead and sodium chloride so that such mixture contains from about 5% to about 65% by weight of liquid, introducing the resulting mixture between opposing solid pressure members of an expressing device, compressing the mixture and compacting the solids between such members under a pressure of from 150 to about 20,000 pounds per square inch, and separating from the compacted solids any liquid expressed from the mixture during the compression.

14. The process for recovering a mixture of lead and salt in a compacted form from an anhydrous sludge consisting essentially of finely-divided lead, from about 0.36 to about 0.38 part by weight of finely-divided sodium 11 chloride. toeachpart oflead', and from about 5% toabout 65% by weightofila liquid. which isa member. ofthe class consisting of tetraethyl lead and. mixtures of. tetraethyl lead and ethyL chloride, which process comprises washing the sludge witliavolatile organic. solventfor thetetraethylv lead which boilsbelow 150 C., incompletely separating. the solvent from the mixture. oi lead and sodium chloride. so that such. mixture contains from. about 5% to about 65% by weight ofiiquid; introducing the result.- ing mixture between opposing. solidpressure members of an expressing device, compressing the mixture and compacting the solids between such members under a pressure of from about 1,000. to about 101(100 pounds per square inch, and separating from the. compacted solids any References Citedinthe file. oi this patent vUNITED SEFA'EES PAIENIS.

696,883 1,149,537 Phillips et a1 Aug. 10,- 1915- 1,218,544 Genter Mar. 6; 1917 1,985,598 Carver Dec. 25-, 1934' 23743047 Stacom Apr. 17, 1945 2,465,704 Aspmau Mar. 29, 1949' m 2,574,759 Rodekohr Nov. 13, 1951' OTHER REFERENCES Chemical Process Industries, by. R Norris Schreve,

published by MCGraw-Hill Book; C.o..of NewY'ork, 1945, 7

liquid expressed ftomthe mixture during the compression. 15 first edition.

Atwood Apr; 1', 1-902- 

4. THE PROCESS FOR RECOVERING A MIXTURE OF LEAD AND SALT IN A COMPACTED FORM FROM AN ANHYDROUS SLUDGE CONSISTING ESSENTIALLY OF FINELY-DIVIDED LEAD, FROM ABOUT 0.36 TO ABOUT 0.38 PART BY WEIGHT OF FINELY-DIVIDED SODIUM CHLORIDE TO EACH PART OF LEAD, AND FROM ABOUT 21% TO ABOUT 51% BY WEIGHT OF A LIQUID WHICH IS A MEMBER OF THE CLASS CONSISTING OF TETRAETHYL LEAD AND MIXTURES OF TETRAETHYL LEAD AND A VOLATILE ORGANIC SOLVENT FOR THE TETRAETHYL LEAD WHICH BOILS BELOW 150* C., WHICH PROCESS COMPRISES INTRODUCING SAID SLUDGE BETWEEN OPPOSING SOLID PRESSURE MEMBERS OF AN EXPRESSING DEVICE, COMPRESSING THE SLUDGE AND COMPACTING THE SOLIDS BETWEEN SUCH MEMBERS UNDER A PRESSURE OF FROM ABOUT 1,250 TO ABOUT 5,000 POUNDS PER SQUARE INCH, AND SEAPRATING FROM THE COMPACTED SOLIDS ANY LIQUID EXPRESSED FROM THE SLUDGE DURING THE COMPRESSION. 